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The Use of Dental Implants in Replacement of Molar Teeth

Thomas J. Salinas, DDS

Removable partial dentures (RPDs) have been traditionally employed for multiple tooth replacement and to restore aesthetics and function in the first and second molar areas most commonly missing teeth.1 Mandibular RPDs can have existing problems related to retention, with tooth wear from clasping components becoming more prevalent related to the age of the denture. Maxillary RPDs typically contain integrity defects, and at least 66% of both maxillary and mandibular prostheses are nonsatisfactory.2

Alternatives to RPDs had not been available until the advent of implants. The success of osseointegrated implants in the partially dentate has been well documented.3 Frequent limitations, however, are apparent from anatomical restrictions from the maxillary sinus or the inferior alveolar canal, and may dictate the use of wider diameter, short implants where success has also been documented.4 Other difficulties of implants placed in the posterior are the result of limited surgical access based upon a reduced interincisal opening, where the risk of neuropraxic injury, malposition, damage to adjacent root structure, and sinus perforation are considerably greater than with the anterior areas.

Some of the literature surveying the necessity of molar replacement becomes of importance in these circumstances. The shortened dental arch (SDA) may be differentially quantified by zero to four pairs of intact premolars or the additional zero to two pairs of opposing molars. It can be concluded from such studies that with intact premolars and at least one pair of occluding molars, there were minimal to no complaints. Those with zero to two pairs of occluding premolars had significant difficulty chewing most foods.5 In other studies, a minority of patients reported difficulty in masticatory performance when utilizing an SDA. Additionally, many of these patients do not experience an improvement of oral comfort by wearing an RPD.6 Furthermore, it has been demonstrated that rehabilitation using either fixed or removable prosthetic reconstruction does not contribute to significant differences in dietary intake.7 A patient satisfaction survey comparing resin-bonded, cantilevered FPDs to conventional RPDs, however, favored the fixed alternative in subjective improvement.8 As a consequence of occlusal stability, extreme SDAs (consisting of zero to two pairs of premolars) exhibited significant spacing and occlusal wear in comparison to more intact arches.9

In light of this literature, it may not be prudent to recreate molar occlusion on the exclusive premise that chewing efficiency will be dramatically improved. Implant replacement of single molar teeth can be targeted at replacement for purposes of retaining function of the opposing teeth or prevention of mesial drift of lower second molars. Re-establishing occlusal function on the basis of multiple missing molars requires advanced treatment planning techniques, further requiring a space analysis and assessment of available bone volume. Additional consideration should be given to risks of ancillary treatment (eg, bone grafting, nerve repositioning) necessary to allow placement of implants. With the ever-increasing age of the population, it becomes apparent that a patient-specific optimal dentition should be considered when treating the elderly within the context of what efficiency an SDA may offer. It can be assumed in those missing molar teeth that function is an absolute goal which embraces preserving existing anatomy while minimizing risk and complications of treatment.